Under-side of the Ross ice shelf in Antarctica is freezing | Daily Mail Online

As long ago as 1973, a study suggested that an ice-free Arctic Ocean could make regions further south colder.

That 'warm Arctic, cold continent' (WACC) pattern is sometimes dubbed 'wacc-y' or 'wacky' among climate scientists.

When unusually warm air enters the region, it melts ice covering the waters of the Arctic Ocean.

This ice normally serves as an insulator, stopping the flow of thermal energy from the water’s surface into the atmosphere.

Without the ice in place, the oceans can transfer a huge amount of this energy into the air above.

This in turn increases air temperatures and this warm air rises up into the upper atmosphere, where it reaches the jet stream.

Jet streams are fast flowing, narrow currents of air that carry warm and cold air across the planet, much like the currents of a river.

They cover thousands of miles as they meander near the tropopause layer of our atmosphere.

The strongest jet streams are the polar jets, found 30,000 to 39,000 ft (5.7 to 7.4 miles/ 9 to 12 km) above sea level at the north and south pole.

In the case of the Arctic polar jet this fast moving band of air sits between the cold Arctic air to the north and the warm, tropical air to the south.

When uneven masses of hot and cold meet, the resulting pressure difference causes winds to form.

During winter, the jet stream tends to be at its strongest because of the marked temperature contrast between the warm and cold air.

The bigger the temperature difference between the Arctic and tropical air mass, the stronger the winds of the jet stream become.

The Arctic polar jet, which can reach speeds of up 200mph (320kph), flows over the middle to northern latitudes of North America, Europe, and Asia and their intervening oceans.

It moves from East to West, although its exact route varies and can be affected by various factors.

With the ice melt in the Arctic and the introduction of warmer air, the route of the jet stream becomes wavier and more erratic.

That means that the colder air it carries from the Arctic can penetrate further south and warmer airs from the tropics is carried further north. 

If the jet stream’s meander buckles south of the UK, it attracts cold air from the Arctic.

Conversely when it swings north, it sucks warm air from the tropics.